Internal combustion engines convert chemical energy, such as gasoline, into mechanical energy. An internal combustion engine compresses a mixture of air and gasoline within a cylinder by use of a piston coupled to a crankshaft. The piston is rotated into a position so as to cause an increase in the mixture density, temperature, and pressure within the cylinder wherein a high voltage electric spark causes the mixture to expand rapidly resulting in movement of the piston. As the piston is moved a connecting rod imparts a linear to rotational movement of the crankshaft to produce the mechanical energy.
The operation of the internal combustion engine involves many parts which produces heat from friction. Excess heat must be removed for engine longevity. However, for efficient operation the internal combustion engine must operate at a predetermined temperature. For this reason, most engines on a vehicle require a cooling system to regulate the engine temperature. Conventionally a radiator is located in the front of the vehicle and positioned transverse to the direction of movement of the vehicle. A radiator fan is then employed to draw air through the radiator so that cooling may be effected when the vehicle is operating at a speed where insufficient air is being driven through the radiator.
A coolant reservoir, also referred to as a coolant recovery tank, allows coolant such as a mixture of water and antifreeze to reside as it expands when heated. The coolant reservoir is typically made of plastic and constructed to allow an operator to visually check the level and condition of the coolant. Conventional coolant systems are sealed and placed under pressure. Late model vehicles pressurize the coolant reservoir essentially eliminating the need for the traditional radiator cap fill port. In this embodiment the cooling system recirculates coolant through the engine and into the radiator for dispersion of excess heat. Should the coolant become heated to the point of expansion, the coolant will expand into the coolant reservoir. This typically occurs when the engine has been turned off immediately after operating. The recirculation discontinues and the coolant reservoir accepts the expansion. As the cooling process takes place after engine shutdown, the coolant begins to shrink within the engine and creates a vacuum that draws the coolant from the reservoir back into the radiator and engine portion of the cooling system. Still more recent engines employ a dual chamber reservoir having a pressurized chamber formed integral with an overflow chamber. Such reservoirs have a pressure relief cap and a fill port cap. The problem with such systems is the cost of manufacturing a dual neck reservoir to hold two caps. Further, the caps are rated at different pressures so there is a possibility of attaching the wrong cap to the vent neck. For instance, one cap may have pressure relieve and the second has no relief. In addition, a second cap located on a coolant reservoir would be located along a side of the reservoir making it very difficult to service.
What is needed in the art is a dual chamber coolant reservoir wherein a single vent neck can be used for coolant insertion and pressure relief.